> f:=arctan(x/y);

> diff(f,x,x)=simplify(diff(f,x,x));

diff(f,x,y)=simplify(diff(f,x,y));

diff(f,y,y)=simplify(diff(f,y,y));

> f:=x^2+y^3-2*x*y-y+4;

> xxx:=solve([diff(f,x),diff(f,y)],[x,y]);

> Student[MultivariateCalculus][SecondDerivativeTest](f,[x,y]=[seq(subs(xxx[i],[x,y]),i=1..2)]);

> Int(x^2*ln(x),x)=int(x^2*ln(x),x);

> Int(sin(x)*cos(x)^2,x)=int(sin(x)*cos(x)^2,x);

>